Method for enhancing growth of mammary parenchyma

ABSTRACT

The growth of milk-producing mammary parenchyma in a mammal can be significantly enhanced by administering to the mammal by intramammary infusion a substance having a mitogenic effect on mammary epithelial cells in said mammal. Good growth enhancement can be achieved using very small quantities of such substances, and in relatively short periods of time.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. Ser. No. 92,009 filed Sep. 2, 1987, now U.S. Pat. No. 5,059,586 which is a continuation-in-part of application Ser. No. 092,009 filed Sept. 2, 1987, now abandoned.

BACKGROUND OF THE INVENTION

Milk production by a mammal is ultimately limited by the amount of mammary parenchyma (secretory tissue) in the mammary gland. Typically, milk yield has been found to be highly correlated with parenchyma wet weight, dry weight, dry fat-free weight and total gland DNA. In 43 Proc. N.Z. Soc. Anim. Prod. 71 (1983), Davis et al attributed increased milk production in genetically superior animals entirely to increased udder volume which is also related to the quantity of parenchyma cells.

Classical evidence indicates that mammary parenchyma growth is directed by pituitary, ovarian, adrenal, placental or locally-derived tissue factors. See Cowie, 15 Mono-graphs on Endocrinology (1980) and U.S. Pat. No. 4,521,409 issued Jun. 4, 1985 to Bauman and Sejrsen, in which it is disclosed that growth of mammary parenchyma in a ruminant can be increased by administering a growth hormone (somatotropin) into the ruminant's blood stream between about the onset of puberty and about the first parturition (preferably about the first conception).

If administered into an animal's blood stream, most mitogens for mammary parenchyma cells bind additionally to receptors in many of the animal's other tissues. Due to such dilution of the desired effect on mammary growth-stimulating receptors, increasing mammary parenchyma via administration into the blood stream would be expected to require relatively large quantities of such mitogens. Hence there is great incentive to develop a practical technique for increasing the milk production capacity and/or efficiency of a mammal that is not dependent on administration into the mammal's blood stream.

Using rabbits, mice and rats that were physiologically abnormal, i.e., ovariectomized and/or pretreated (e.g. with a reproductive hormone) to induce psueudopregnancy, studies have been made of effects on mammary gland development by subcutaneous injection of a somatotropin and/or other hormones, implants that released cholera toxin, or intraductal injection of "lactogenic hormone". Lyons et al, 50 Proc. Soc. Exper. Biol. Med. 308-11 (1942) and 14 Recent Prog. Hormone Res. 219-54 (1958); Fiddler et al, 49 J. Endocrin. 459-69 (1971); Daniel et al, 224 Sci. 1245-47 (1984); and Silberstein et al, 81 Proc. Natl. Acad. Sci. USA 4950-54 (1984). Based on other studies using rabbits that were pregnant or pretreated (e.g. with a reproductive hormone) to induce pseudopregnancy, it has been reported that intraductal injection of prolactin or ("lactogenic hormone" induced lactation. Bradley et al, 14 J. Endocrin. 28-36 (1956) and Meites et al, 150 Amer. J. Physiol. 394-99 ( 1947). Others have studied in vitro effects of mitogens such as an epidermal growth factor, with or without insulin, on the growth of cultured mammary cells of various animal species. Imagawa et al, 79 Proc. Natl. Acad. Sci. USA 4074-77 (1982); Taketani et al, 113(3) Endocrin. 871 (1983) and 80 Proc. Natl. Acad. Sci. USA 2647-50 (1983); Tonelli et al, 285 Nature 250-52 (1980); and Turkington, 57 Exper. Cell Res. 79-85 (1969). The disclosures cited in this paragraph are incorporated here by reference.

OBJECTIVES OF THE INVENTION

It is an object of this invention to provide a method which enhances the growth of mammary parenchyma in a female mammal, and thereby significantly increases the milk production capacity and/or efficiency of such a mammal. Another object is such a method having a high degree of specificity in the mammal for the desired increase in parenchyma. Another object is a method requiring use of a small (preferably minimal or near-minimal) quantity of a substance effecting such an enhancement in parenchyma growth. Another object is such a method which can be carried out conveniently. Another object is a method that provides predictably uniform growth-enhancement effects on treated mammary glands in the animal. Another object is a method having little potential for biological side effects in the animal. Other objects are various compositions suitable for convenient and commercially practical use in such methods. These and other objects of the invention will be more fully apparent from the following detailed disclosure.

SUMMARY OF THE INVENTION

We have discovered that these objectives can be achieved in female mammals by intramammary infusion of a substance having a mitogenic effect on mammary epithelial cells in that mammal. Surprisingly, substantial enhancement of normal parenchyma growth can be achieved by this method which does not require administration into the animal's blood stream, subcutaneous injection or implantation, but instead utilizes a convenient administration technique of a kind which, in the case of most dairy cows and some other mammals, has been routinely carried out for infusion of antibiotics. Substantial enhancements of parenchyma growth, and consequently milk production capacity of the mammal over those normally observed can be achieved by this invention utilizing only very small quantities of such substances, and in relatively short intervals of time. These discoveries were quite unexpected, largely because there was no prior art known to indicate that such substances would readily pass from the teat cistern of a mammary gland into contact with cells subject to the mitogenic effects needed to substantially enhance growth of the gland.

DESCRIPTION OF THE INVENTION

This invention is useful for any female mammal in which an increase in mammary parenchyma growth is desired. It is especially useful for ruminants, including cattle such as dairy cows, cows bred primarily for beef production, and heifers of dairy and beef cattle breeds. It is useful in all known breeds of dairy cows, e.g. Holstein, Friesien, Brown Swiss, Jersey, Guernsey, Ayrshire, Milking Shorthorn, and crossbreeds thereof, and in all known breeds of beef cows, e.g. Hereford, Angus, Zebu, Charolais, Brangus, Simmental, Chianina, Dutch Belted, Limousin, and crossbreeds thereof. It is also useful in other ruminants, e.g. sheep and goats of all breeds, as well as various non-ruminants, e.g. swine of all breeds. Most commonly, the invention is used for treatment of mammals that are physiologically normal which, for present purposes, means not ovariectomized and not pretreated (e.g. with a reproductive hormone such as estrogen, gonadotrophin or the like) to induce pseudopregnancy or puberty.

As used herein, the term "mammary parenchyma" refers to tissue in a mammary gland (including that commonly called "mammary epithelium") which is instrumental in production of ilk by that gland. Typically in the female, mammary gland growth occurs mainly after the onset of puberty. Usually (e.g. in the heifer) most mammary gland growth occurs during the first gestation. Further growth and/or regrowth of the parenchyma occurs during subsequent gestations. Normally, the mitosis (cell division) causing such growth must be accompanied or followed by sufficient differentiation of the new cells that, following parturition, they will contribute to milk production.

To enhance such growth, this invention can be carried out by administering the substance having the desired mitogenic effect to the mammal between about the onset of puberty (including the peripubertal period) and the mammal's first gestation, or during the first or any subsequent gestation. Thus, typically such administration is carried out in a "dry" period, i.e., while the mammal is non-lactating. In pregnant dairy cows and similar mammals, administration during the last trimester before parturition is usually advantageous. The most preferred intervals for such administration depend on various factors, including the particular substance employed to achieve the desired mitogenic effect. Further details useful in identifying such preferred intervals are set forth hereinafter.

The convenient and surprisingly effective administration technique of this invention is most commonly called intramammary infusion. In mammals such as cows, this technique is routinely used to administer antibiotic-containing ointments or other formulations for prevention or control of mastitis. In practice of this invention, the substance having a mitogenic effect usually can be administered by a similar technique or, even more conveniently, by including it (with or without another parenchyma growth stimulant) in a formulation to be infused for mastitis prevention or control, or for any other purpose.

In this technique, a blunt-tip syringe is inserted through the teat orifice and streak canal such that the substance having a mitogenic effect is deposited in the teat cistern. From there, it normally spreads through the teat cistern, gland cistern and ductal system of the mammary gland. This well-known technique is described in "Drugs in Veterinary Practice", pp. 80-83, by Spinelli et al, C. V. Mosby Co., St. Louis, Mo. (1978) and U.S. Pat. No. 4,011,312 issued Mar. 8, 1977 to Reuter et al, both incorporated here by reference. For purposes of this invention, other procedures should be considered equivalents of intramammary infusion to the extent they deposit such a substance in the teat cistern and thereby result in spreading of same through the ductal system and passage therefrom into mammary tissue where it has an enhancing effect on parenchyma growth.

For purposes of this application, "direct" and "paracrine" mitogenic effects are to be understood as effects that do not require, and in most instances do not involve, the infused substance entering the treated animal's blood stream in an amount that raises its concentration therein to a level sufficient to have, through endocrine regulation, a mitogenic effect of the desired magnitude on parenchyma cells in the animal. For a review of paracrine regulation of mammary gland growth, see Oka et al, 15(1) Clinics in Endocrin. and Metab. 79-97 (1986).

This invention can be carried out using any substance having a significant direct or paracrine mitogenic effect on mammary parenchyma in the mammal to be treated. Many important embodiments are carried out using a substance which acts directly on mammary parenchyma cells in the infused gland to increase their rate of normal cell proliferation. In other embodiments, the substance acts directly on nonparenchyma cells within the gland resulting in such cells providing, through a paracrine effect, a locally increased amount of a substance having a direct mitogenic effect on mammary parenchyma cells in the infused gland.

In some instances, as can be seen from Examples 14-16 hereinafter, intramammary infusion of such a substance results in substantial growth of mammary glands adjacent to those infused, and without a significant increase in the level of the infused substance in the animal's bloodstream. However, sufficient receptors for direct or paracrine effects of some substances within a mammary gland may exist only during certain phases of the animal's physiology. For example, there appear to be a greater number of somatotropin-binding receptors in the bovine mammary gland during gestation than when the animals are not pregnant. Compare L'HORMONE PLACENTAIRE SOMATOMAMMOTROPE BOVINE (Chapter V) by Jean-Francois Beckers, Universite de Liege, Faculte de Medecine Veterinaire (1983) with Hormonal Control of Casein Synthesis and Organ Culture of the Bovine Lactating Mammary Gland, Gertler et al, 49 J. Dairy Res. 387 (1982) and Lactogenic Hormones: Binding Sites, Mammary Growth, Secretory Cell Differentiation, and Milk Biosynthesis in Ruminants, Akers, 68 J. Dairy Sci. 501 (1985).

In many embodiments of the invention, the substance having a mitogenic effect is a polypeptide growth factor. Certain classes of such growth factors preferred for use in this invention have molecular weights generally lower than about 65,000, even more typically lower than about 23,000 and, in the case of growth factors having a direct mitogenic effect as described hereinbefore, typically lower than about 10,000. Some non-polypeptide substances, e.g. ovarian and placental steroids and agonists thereof, can be suitably employed in some instances. In either case, the substance may be naturally occurring, synthesized to simulate a naturally occurring substance, or synthesized to provide a substance that is unlike any naturally occurring compound but nevertheless has such a mitogenic effect.

A preferred class of polypeptide growth factors that can be used are the epidermal growth factors (EGF's). Typically, these interact with receptors on mammary epithelial cells to stimulate proliferation of such cells. EGF's of various mammalian species have been sequenced and identified by their amino acid sequences and/or configurations dictated by internal cross-linking of cysteine residues through disulfide bonds. One such EGF is a well-characterized single-chain polypeptide of 53 amino acids which can be isolated from submaxillary (salivary) glands of adult male mice. Another form of EGF, human urogastrone, is synthesized in the duodenum and salivary glands and can be isolated from human urine. Urogastrone is 70% homologous (37 of 53 common amino acids) with mouse EGF and has three disulfide bonds in the same positions. Available data indicate that human urogastrone and human EGF are identical. Bovine EGF, which can be synthesized chemically or in a microorganism (e.g. bacteria such as E. coli) or eucaryotic cell culture by use of recombinant DNA, is believed to have an amino acid sequence essentially as follows: Asn-Phe-Leu-Lys-Lys-Cys-Phe-Pro-Glu-Gyr -Thr-Pro-Asn-Phe-Glu-Gly-Tyr-Cys-Leu-Asn-Gly-His-Val -Cys-Ile-Tyr-Phe-Gly-Ile-Ala-Asn-Leu-Phe-Ser -Cys-His-Cys-Pro-Ile-Gly-Tyr-Pro-Gly-Lys-Arg-Gly -Glu-Tyr-Ile-Asp-Phe-Asp-Gly-Trp-Asp-Pro-His. For more information on EGF's, see "Epidermal Growth Factor" by Carpenter et al, 48 Ann. Rev. Biochem. 193-216 (1979) and Gregory, 257 Nature 325- 27 (1975) both incorporated here by reference.

It is known that the entire amino acid sequence of human or mouse EGF is not necessary for mitogenic activity. E.g., U.S. Pat. No. 3,917,824 issued Nov. 4, 1975 to Gamble et al discloses molecular variations shortened (e.g. by 2, 5 or 6 amino acids) at the carboxy terminus; U.S. Pat. No. 4,035,485 issued Jul. 12, 1977 to Gregory et al discloses a molecular variation shortened by 7 amino acids; U.S. Pat. No. 3,948,875 issued Apr. 6, 1976 to Cohen discloses EGF derivatives lacking the C-terminal Leu-Arg residues; PCT Appln. WO 83/04030 by Banks et al discloses urogastrone analogs that differ in identity or location of one or more amino acids; and PCT Appln. WO 85/01284 by Komoriya et al discloses polypeptides having EGF-like activity based on the presence of a ten-amino acid sequence corresponding to that between Cys₂₀ and Cys₃₁ of natural EFG; each incorporated herein by reference. To the extent these or similar molecular variations of EGF, analogs thereof, or other compounds that interact with EGF (or functionally similar) receptors in the mammary gland following intramammary infusion and achieve objectives of this invention in substantial measure, they are equivalents of EGF's for purposes of this invention.

Various procedures for preparing an EGF are known. E.g., Japanese Patent Appln. 59/027858 (Nippon Shinyaku) discloses condensing protected 1-5 amino acid peptides to form a protected tripentacontapeptide which is oxidized, after being deprotected, to make an EGF; European Patent Appln. 128,733 by Lee et al published Dec. 19, 1984 and Patent Appln. WO 85/00369 by Bell published Jan. 31, 1985 disclose EGF preparations by expression of recombined DNA; British Patent 2,092,155 to Sugimoto discloses production of an EGF by multiplying hybridoma cells; and U.S. Pat. No. 4,528,186 issued Jul. 9, 1985 to Nishimura et al discloses recovery of an EGF from human urine. These disclosures are incorporated by reference.

In other preferred embodiments, the growth factor can be selected from fetal EGF's such as the alpha-type transforming growth factors. See European Patent Applns. 105,014 by Sporn et al and 190,018 by Todaro et al (disclosures incorporated here by reference). Typically, these interact with receptors in the mammary gland to provide the desired mitogenic activity. Another class of the various polypeptides useful in this invention is illustrated by the viral protein analogs disclosed in European Patent Appln. 199,769 based on WO 86/02650 by Brown et al.

In other embodiments, the growth factor can be a polypeptide from the insulin family, an analog of such a polypeptide or another substance that interacts with insulin-like growth factor (IGF) or functionally similar receptors in the mammary gland to provide a mitogenic effect on the parenchyma. Preferably, the IGF employed is an IGF-I ("somatomedin") or IGF-II. Similar results can generally be obtained using insulin or a precursor thereof (e.g. pro-insulin) although the amounts required are much greater than those of an IGF.

There is extensive literature on identities of these insulin family growth factors and methods for their production. For example, amino acid sequences for human IGF-I and -II and their production by expression of recombinant DNA in microbial hosts are described in European Patent Applns. 128,733 (supra) and 123,228 (Chiron Corp.) published Oct. 31, 1984. IGF-I analogs having valine in amino acid position 59 are described in European Patent Appln. 158,892 by Niwa et al published Oct. 23, 1985. More information on IGF's can be found in Rinderknecht et al, 73 Proc. Natl. Acad. Sci. USA 2365 (1976); Zapf et al, 19 Curr. Top. Cell. Reg. 257 (1981); and Wilson et al, 95 J. Endocrin. 59-64 (1982). Preparations of insulin and pro-insulin are described in Johnson, 219 Sci. 632-37 (1983) and European Patent Appln. 55,945 (Genentech) published Jul. 14, 1982. The disclosures cited in this paragraph are incorporated here by reference.

In other preferred embodiments, the substance to be infused can be selected from one or a mixture of the various compounds in the arachidonic acid metabolic pathway and analogs thereof that have a mitogenic effect on mammary epithelial cells. These include the prostaglandins (such as those of the A to F series) and their analogs, e.g. [11α, 13E,15S]-11,15-Dihydroxy-9-oxoprosta-13-en-1-oic acid (E₁), [5Z,11α,13E,15S]-11,15-Dihydroxy-9-oxoprosta-5,13-dien-1-oic acid (A.sub.), [5Z,13E,15S]-15-Hydroxy-9-oxoprosta-5, 10,13-trien-1-oic acid (A₂), [13E,15S]-15-Hydroxy-9-oxoprosta-8[12],13-dien-1-oic acid (B₁), [5Z,13E, 15S]-15-Hydroxy-9-oxoprosta-5,8[12],13-trien-1-oic acid (B₂), [5Z,9α,13E,15S]9,15-Dihydroxy-11-oxoprosta-5,13-dien-1-oic acid (D₂), [9α,11α,13E, 15S]-9,11,15-Trihydroxyprost-13-en-1-oic acid (F₁ α), [5Z,9α,11α,13E,15S]-6,9-Epoxy-11,15-dihydroxyprosta-5,13-dien-1-oic acid (I₂), all available from Sigma Chemical Co., St. Louis, Mo., Lutalyse® prostaglandin (F₂ α) available from The Upjohn Co., Kalamazoo, Mich. and cloprostenol. Precursors and metabolites of these substances (e.g. arachidonic acid and its metabolites) that are similarly active in effecting mammary cell mitosis can also be used, and those with greater activity and/or longer half life can be used in correspondingly lower doses. Many of these substances are described in Advances in Prostaglandin, Thromboxane, and Leukotriene Research, Vol. 14 (especially pp. 1-43, 73-129 and 263-307) edited by J. E. Pike and D. R. Morton, Jr., Raven Press, New York, N.Y. (1985), and Prostaglandins and the Arachidonic Acid Cascade, Norman A. Nelson, et al, 60 Chem. Eng. News, p. 30 et seq (Aug. 16, 1982), both incorporated here by reference.

In other embodiments, the growth factor can be one or a mixture of the mammary-derived or mesenchyme-derived growth factor (MDGF) polypeptides described by W. R. Kidwell et al in 260(9) J. Biol. Chem. 5745-52 (1985) and 46 Cancer Res. 933-39 (February, 1986), the disclosures of which are incorporated here by reference. These MGDF's can be obtained by purification from milk or mammary tumors in accordance with procedures disclosed in those publications.

Substances that can be infused to achieve a paracrine mitogenic effect include placental lactogens, certain anterior pituitary hormones such as somatotropins, and other polypeptides having sufficiently similar chemical structure to provide essentially similar mitogenic effect(s) for purposes of this invention. Placental lactogens of specified mammalian species can be obtained by purification from their placental tissues. Bovine placental lactogen, which can be synthesized by use of recombinant DNA in microorganisms or cell cultures, has the amino acid sequence essentially as follows: ##STR1## Further information about bovine placental lactogen, its production and biological activity can be found in U.S. patent application Ser. No. 092,116 by John C. Byatt et al filed concurrently with this application, now abandoned. Bovine, ovine, porcine, human and other somatotropins can be obtained by various published procedures including that described in European Patent Appln. 177,478 published Apr. 9, 1986 (see Examples 40-41).

As aforesaid, infusion of a substance having a mitogenic effect in accordance with this invention should be completed far enough in advance of parturition that the resulting mammary tissue has adequate opportunity to differentiate into milk-producing cells. For substances having a direct mitogenic effect, e.g. IGF's, EGF's, prostaglandins, MDGF's, TGF-α's, insulins and combinations thereof, such infusion is most advantageously completed prior to about the last 5 (preferably 10) days of the mammal's pregnancy. When the substance is one providing a paracrine mitogenic effect, e.g. a somatotropin, placental lactogen or a mixture thereof, its administration can usually be continued until about 5 days before parturition without significantly detracting from the desired effect, although such administration during about the last 10 days of pregnancy may not substantially enhance that effect.

The amounts of the mitogenic activity-providing substance required by the present invention are very small, indicating an unexpectedly high efficiency in their use. For substances having a direct mitogenic effect, useful units doses for infusion of a gland may be no more than about 100 micrograms, and smaller doses may be effective in some instances. Unit doses up to about 10 milligrams or more can usually be administered without interfering with the desired effects, but doses less than about 1 milligram are generally preferable for economic reasons. In the case of substances having a paracrine mitogenic effect, such unit doses can be as little as about 10 milligrams, and smaller doses can be effective in some cases. Unit doses of such substances up to about 200 milligrams or more can generally be used without intolerably diminishing the desired effect, but doses less than about 100 milligrams are usually economically preferred.

The most desirable doses, frequencies and numbers of infusions can be determined by routine experimentation. Commonly, spacing treatments over as long a period as possible tends to afford maximum results, provided sufficient time remains thereafter for differentiation of the new parenchyma cells before parturition. In many cases, from 1 to about 5 successive infusions provide good results. These can be suitably spaced by, e.g., from 1 to about 10 (preferably from 2 to about 5) days. The fact that substantial increases in parenchyma growth can be achieved in such short periods of time was quite unexpected and has considerable commercial significance. Satisfactory total doses, i.e., the sum of the successive infusions of an individual mammary gland during a gestation or puberty prior to gestation, are generally at least about 100 micrograms, typically less than about 50 milligrams, and often preferably less than about 5 milligrams of a substance providing a direct mitogenic effect. For a substance having a paracrine mitogenic effect, satisfactory total doses are generally at least about 10 milligrams and typically less than about 500 milligrams.

Other substances that furnish effects essentially similar to those afforded by any of the various mitogenic activity-providing substances mentioned herein can be likewise used in this invention, if desired. While the invention can be practiced using a single mitogenic activity-providing substance, combinations of such substances may be advantageous in some instances. In many embodiments, it is desirable to infuse a mitogenic activity-providing substance corresponding closely to a substance naturally occurring in the species to be treated, e.g. a bovine EGF, IGF, placental lactogen and/or somatotropin for treatment of cattle. However, substances corresponding to those naturally occurring in other species are commonly also suitable.

Normally, the method of this invention is carried out using a composition adapted for administration to a mammal by intramammary infusion and containing an amount, effective to enhance the growth of mammary parenchyma in said mammal, of a substance having a mitogenic effect on mammary epithelial cells in that mammal. Such compositions should be physiologically tolerable, preferably substantially nonirritating and essentially free of endotoxins. If desired, the mitogenic activity-providing substance can be infused as a solid which may be finely divided or compressed in an advantageous shape and size, e.g. for prolonged release in the teat cistern. In other embodiments, it is desirable to use a vehicle that is substantially liquid at the mammal's body temperature, and preferably also at the ambient temperatures of infusion. Whether the infused composition is solid or fluid, it is normally advantageous for it to include a vehicle that enhances diffusion of the mitogenic activity-providing substance through the mammary gland. In some, but not all cases, it is advantageous for the vehicle to be substantially water-soluble. In most cases, it is advantageous to use a vehicle in which the mitogenic activity - providing substance is substantially soluble.

The most desirable type and quantity of vehicle for infusion of the mitogenic activity-providing substance can be determined by routine experimentation. To illustrate, 1-10 ml of a liquid vehicle having a pH in the physiological range, e.g. a physiological saline solution, Freund's Incomplete Adjuvant or a vegetable (e.g. peanut or sesame) or mineral oil, is typically satisfactory. Emulsions of two or more of such vehicles are commonly advantageous. Appropriate stabilizers, e.g. mono- and/or disaccharides, sugar and alcohols or neutral amino acids, may be included if desired.

This invention also provides a process for preparing compositions useful for enhancing the growth of mammary parenchyma in a mammal. In a generic embodiment, such a process comprises combining (e.g. dispersing) a substance having a mitogenic effect on mammary epithelial cells in said mammal in a vehicle that enhances diffusion (and preferably prolongs release) of the substance through a mammary gland of said mammal, said composition being adapted by said combining for administration to the mammal by intramammary infusion.

The following descriptions of specific embodiments of the invention rae illustrative only and do not imply any limitation on the scope of the invention. All animals in these examples were physiologically normal (as defined hereinbefore). All temperatures are in degrees Celsius. Parts and percentages are by weight except where otherwise indicated.

A. Epidermal Growth Factors EXAMPLES 1-2

12 pregnant, non-lactating, cross-bred beef cows within their last 40-80 days of gestation were housed in a free-stall facility, fed a ration of alfalfa hay and pelleted concentrate, and administered 10 ml of an excipient (Freund's Incomplete Adjuvant emulsified with an equal volume of 0.9% sterile saline) into each quarter-udder by intramammary infusion through the streak canal on days 1, 3, 5, 7 and 9 of this study. Infusions were carried out using a 3.2 centimeter long, approximately 12 gauge, blunt-tipped plastic teat infusion cannula obtained from Jorgensen Laboratories, Loveland, Co. Because front and rear udder halves are not of equal size, treatment vs. control comparisons were made between laterally opposite quarters, i.e., front right vs. front left and rear right vs. rear left. Treatments were randomly assigned to right or left udder-halves, with the contralateral half serving as its control. In the treatment infusions, the excipient contained 25 micrograms of human EGF (hEGF) obtained from G. D. Searle & Co., Ltd., U.K. (6 animals) or mouse EGF (mEGF) obtained from Collaborative Research Corp., Lexington, Mass. (the other 6 animals). The hEGF had been prepared by Searle by expression of recombinant DNA and subsequently further purified by filtration on a 10,000 MW filter to a purity above 90% determined by HPLC. The mEGF was culture-grade, Catalog No. 40001, from mouse submaxillary glands, prepared by the method of Savage et al, 247 J. Biol. Chem. 7609 (1972) with a purity of 98% determined on SDS polyacrylamide gel.

Prior to treatment, each animal was teat-dipped for 3 consecutive 14 and each teat was pre-cleaned with 70% ethanol in water on the day of treatment. On day 14 the cows were sacrificed and their mammary glands excised. Each udder (milked out if necessary) was skinned, divided along the median suspensor ligament and then into front right, front left, rear right and rear left udder quarters. Each quarter-udder was ground, a representative 200 gm sample was homogenized with 4 times its volume of water, and the total homogenate volume of each was measured.

To determine dry weight of each quarter-udder, three 10 ml aliquots of a 1:5 diluted homogenate were placed in pre-weighed pans, dried overnight at 60° and then dried and weighed to a consistent value.

To determine dry fat-free tissue weight of each quarter-udder, three 5 ml aliquots of the undiluted homogenate were extracted by the method of Anderson, 41 J. Anim. Sci. 118 (1975) except that samples were placed in pre-weighed 25×150 mm glass centrifuge tubes and extracted overnight with 10 ml ethanol:ether (3:1), then centrifuged (5 min at 500 rpm) and the supernatant aspirated; an additional 10 ml aliquot of ethanol:ether was added for a second extraction; and the sample was dried under nitrogen until a consistent value was obtained.

DNA in each quarter-udder was determined by the method of Burton, 12B methods in Enzymol. 163-66 (1968) using an assay solution of 15% trichloroacetic acid (TCA) in 2N HCl. In these determinations, aliquots of gland homogenate were diluted 1:5 with water and rehomogenized. Using triplicate 0.25 ml or 0.5 ml aliquots of these homogenates, each aliquot was mixed with 2 ml of the assay solution. After 30 min, the samples were centrifuged for 10 min at 3000 rpm and the resulting pellets were washed with 2 ml of a 10% solution of TCA in distilled water. After recentrifugation, the resulting pellets were disrupted in 2 ml of 0.5N perchloric acid and heated for 30 min at 70° to extract DNA. Samples were centrifuged and 1 ml of each resulting supernatant was placed in a 12×75 mm tube. After addition of 2 ml of a solution of 1.5 g diphenylamine and 1.5 ml H₂ SO₄ in 100 ml glacial acetic acid (and 0.1 ml of 1.6% aqueous acetaldehyde per 20 ml reagent just prior to use), the samples were vortexed and incubated overnight at 27°. Calf thymus DNA was the standard.

                  TABLE 1                                                          ______________________________________                                         Effects of Intramammary Infusion of hEGF                                       on Quarter-Udders in Pregnant Beef Cows                                                  Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   389.9    120.0  63.2     794.5                                     Mean                                                                       B.  Control Mean                                                                               357.3    111.4  58.3     710                                       (Excipient only)                                                           C.  Mean Increase                                                                              32.6     8.6    4.9      84.5                                      (A - B)                                                                    D.  % Increase, 9.1      7.7    8.4      11.9                                      (A - B)/B                                                                  E.  Avg % In-   12.9     13.1   16.1     14.8                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.01     0.09   0.16     0.06                                      % Increase, p<                                                             ______________________________________                                    

                  TABLE 2                                                          ______________________________________                                         Effects of Intramammary Infusion of mEGF                                       on Quarter-Udders in Pregnant Beef Cows                                                  Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   419.6    150.2  69.6     905.1                                     Mean                                                                       B.  Control Mean                                                                               402.0    147.9  64.6     794.9                                     (Excipient only)                                                           C.  Mean Increase                                                                              17.6     2.3    5.0      110.2                                     (A - B)                                                                    D.  % Increase, 4.4      1.6    7.9      13.8                                      (A - B)/B                                                                  E.  Avg % In-   1.8      2.1    5.2      12.0                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.22     0.40   0.19     0.05                                      % Increase, p<                                                             ______________________________________                                    

As shown in Tables 1 and 2, quarter-udders infused with hEGF or mEGF were consistently heavier and contained more DNA than their laterally-opposite control quarters that received excipient only, and at generally high levels of statistical significance.

EXAMPLES 3-6

24 pregnant, non-lactating, cross-bred beef cows within their last 40-80 days of gestation were randomly divided into 4 treatment groups with 6 animals in each group. The effects of intramammary infusion of human EGF on quarter-udders in these animals were determined as described in Example 1 except that (A) as the excipient, the Freund's emulsion was used for Group 1 and an emulsion containing 60 parts sesame oil and 40 parts injectable grade 0.9% sterile saline containing 0.5T Tween-20 was used for Groups 2, 3 and 4 and (B) the amounts of hEGF included in each treatment infusion were 25 micrograms for Groups 1 and 2, 2.5 micrograms for Group 3, and 250 micrograms for Group 4. DNA determinations were made as in Examples 1-2 except that the initial triplicate 0.5 ml aliquots of homogenate were extracted with 2 ml of ethanol:ether (3:1) for 1 hour, centrifuged for 15 min at 3000 rpm, washed with 2 ml of 70% ethanol for 10 min, centrifuged at 3000 rpm for 15 min and aspirated of ethanol prior to mixing of each aliquot with the TCA solution. Results for Groups 1-4 are in Tables 3-6, respectively.

                  TABLE 3                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 125 Micrograms                  of hEGF in Freund's Emulsion on Quarter-Udders in Pregnant                     Beef Cows (Group 1)                                                                      Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   364.9    107.2  60.3     723.0                                     Mean                                                                       B.  Control Mean                                                                               349.5    101.0  56.8     629.0                                     (Excipient only)                                                           C.  Mean Increase                                                                              15.4     6.2    3.5      94.0                                      (A - B)                                                                    D.  % Increase, 4.4      6.1    6.2      14.9                                      (A - B)/B                                                                  E.  Avg % In-   8.1      10.3   8.3      23.0                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.15     0.11   0.13     0.18                                      % Increase, p<                                                             ______________________________________                                    

                  TABLE 4                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 125 Micrograms                  of hEGF in Sesame Emulsion on Quarter-Udders in Pregnant                       Beef Cows (Group 2)                                                                      Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   370.2    122.1  71.0     995.0                                     Mean                                                                       B.  Control Mean                                                                               356.2    111.1  68.8     703.0                                     (Excipient only)                                                           C.  Mean Increase                                                                              14.0     11.0   2.2      292.0                                     (A - B)                                                                    D.  % Increase, 3.9      9.9    3.2      41.5                                      (A - B)/B                                                                  E.  Avg % In-   10.4     20.2   15.9     70.0                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.2      0.02   0.3      0.09                                      % Increase, p<                                                             ______________________________________                                    

                  TABLE 5                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 12.5 Micrograms                 of hEGF in Sesame Emulsion on Quarter-Udders in Pregnant                       Beef Cows (Group 3)                                                                      Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   397.8    132.4  79.4     867.6                                     Mean                                                                       B.  Control Mean                                                                               400.0    127.0  72.7     896.6                                     (Excipient only)                                                           C.  Mean Increase                                                                              (2.2)    5.4    6.7      (29.0)                                    (A - B)                                                                    D.  % Increase, (0.5)    4.2    9.2      (3.3)                                     (A - B)/B                                                                  E.  Avg % In-   0.6      7.8    16.3     (2.2)                                     crease/Animal                                                              F.  Sig. Level of                                                                              --       0.17   0.1      --                                        % Increase, p<                                                             ______________________________________                                    

                  TABLE 6                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 1.25 Micrograms                 of hEGF in Sesame Emulsion on Quarter-Udders in Pregnant                       Beef Cows (Group 4)                                                                      Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   391.9    131.5  81.7     733.2                                     Mean                                                                       B.  Control Mean                                                                               360.2    117.9  75.1     729.2                                     (Excipient only)                                                           C.  Mean Increase                                                                              31.7     13.6   6.6      4.0                                       (A - B)                                                                    D.  % Increase, 8.8      11.6   8.8      0.5                                       (A - B)/B                                                                  E.  Avg % In-   9.9      12.2   11.9     1.6                                       crease/Animal                                                              F.  Sig. Level of                                                                              0.001    0.004  0.03     --                                        % Increase, p<                                                             ______________________________________                                    

As shown in Tables 3-6, quarter-udders infused with hEGF were generally substantially heavier and contained more DNA than their laterally-opposite quarters that received excipient only.

EXAMPLES 7-8

24 pregnant, non-lactating, cross-bred beef cows within their last 40-80 days of gestation were randomly divided into 3 treatment groups with 8 animals in each group. The effects of intramammary infusion of human EGF on quarter-udders in these animals were determined as described in Examples 1-2 except that the amounts of hEGF included in each treatment infusion were 25 micrograms for Group 1, 250 micrograms for Group 2, and 2.5 micrograms for Group 3. Gland weights and DNA were determined as in Examples 1-2. Results with the low dose used for Group 3 were obscured by swellings of some glands. Results for Groups 1 and 2 are in Tables 7 and 8, respectively.

                  TABLE 7                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 125 Micrograms                  of hEGF on Quarter-Udders in Pregnant Beef Cows (Group 1)                                Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   363.0    113.0  52.8     396.9                                     Mean                                                                       B.  Control Mean                                                                               358.0    109.7  50.7     358.9                                     (Excipient only)                                                           C.  Mean Increase                                                                              5.0      3.3    2.1      38.0                                      (A - B)                                                                    D.  % Increase, 1.5      3.0    4.1      10.6                                      (A - B)/B                                                                  E.  Sig. Level of                                                                              0.34     0.21   0.16     0.12                                      % Increase, p<                                                             ______________________________________                                    

                  TABLE 8                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 1.25 Micrograms                 of hEGF on Quarter-Udders in Pregnant Beef Cows (Group 2)                                Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   392.5    122.0  63.8     344.0                                     Mean                                                                       B.  Control Mean                                                                               388.2    115.7  61.4     384.0                                     (Excipient only)                                                           C.  Mean Increase                                                                              4.3      6.3    2.4      (40.0)                                    (A - B)                                                                    D.  % Increase, 1.1      5.3    3.9      (10.4)                                    (A - B)/B                                                                  E.  Sig. Level of                                                                              0.4      0.12   0.26     --                                        % Increase, p<                                                             ______________________________________                                    

As shown in Tables 7-8, quarter-udders infused with hEGF were heavier than their laterally-opposite quarter-udders that received excipient only.

EXAMPLES 9-12

When dairy or beef heifers (either pregnant or nonpregnant) or pregnant dairy or beef cows within their last 25-60 days of gestation are infused using the procedures and dosages of Examples 3-6 with bovine EGF, results are essentially the same, i.e. substantial and statistically significant increases in the weights and DNA of the treated quarter-udders.

EXAMPLE 13

48 pregnant holstein heifers within their last 40 days (approximately) of gestation were housed in a free-stall facility, fed a ration of alfalfa hay and pelleted concentrate, and administered 10 ml of an excipient into each quarter-udder by intramammary infusion through the streak canal every third day until parturition with the exception of one animal which was treated with human EGF as described in this Example only until 15 days before parturition. Infusions were carried out using a 3.2 centimeter long, approximately 12 gauge, blunt-tipped plastic teat infusion cannula obtained from Jorgensen Laboratories, Loveland, Co. Animals were randomly assigned to each of the following 4 treatments (12 animals each): (A) 250 micrograms of human EGF obtained from G. D. Searle & Co., Ltd. (U.K.), solubilized (62.5 micrograms/ml) in sterile, injectable grade 0.9% saline containing 0.5% Tween-20 and then emulsified just prior to use in sterile sesame oil containing 5% Arlacel A mannide monooleate (3:2 oil: saline) with a final concentration of 25 micrograms/ml of hEGF in the excipient; (B) 250 micrograms of bovine IGF-I prepared as in Examples 14-16, purified and then solubilized and emulsified as just described for hEGF; (C) 50 milligrams of N-methionyl bovine and somatotropin (BST) prepared as in Examples 40-41 and then diluted to 10 mg/ml in sterile sesame oil; and (D) a control using excipient (sterile sesame oil) alone. In each animal, all 4 quarter-udders received the same treatment. Each udder was sprayed with 70% ethanol and wiped dry prior to treatment and dipped with an iodine solution following treatment. At parturition, 4 animals from each treatment group were sacrificed and their mammary glands were removed for analysis. The other 8 animals from each treatment group were milked normally each a.m. and p.m. for the first 105 days of lactation.

During those 105 days, the animal treated with hEGF only until 15 days before parturition produced an average of 9.6 kg milk/day (34.8%) more than the average produced by the 8 control cows. On average, milk production by the cows treated until parturition did not exceed that of the control cows.

B. Insulin-like Growth Factors EXAMPLES 14-16

24 pregnant, non-lactating, cross-bred beef cows within their last 40-80 days of gestation were housed in a free-stall facility, fed a ration of alfalfa hay and pelleted concentrate, and administered 10 ml of an excipient (a sesame oil emulsion of the kind used in Examples 4-6) into each half-udder by intramammary infusion through the streak canal on days 1, 3, 5, 7 and 9 of this study. The infusion technique, random assignment of half-udders to treatment or control, and treatment vs. control comparisons were as in Examples 1-2. In the treatment infusions, the excipient contained bovine insulin-like growth factor-I (bIGF-I) prepared by expression in E. coli (Prla Strain 079) of recombinant DNA coding for bIGF-I fused to the "lam" B cell wall protein signal sequence, secretion into the E. coli periplasmic space, and recovery/purification by conventional techniques including gel filtration, cation exchange and reverse-phase HPLC. This bIGF-I had the same amino acid sequence and secondary structure as the AMgen human IGF-I used in Example 20. In standard L6 myoblast assays, its activity was essentially the same (90-123%) as that of the Example 20 hIGF-I. The amounts of bIGF-I in each infusion were: Group 1--2.5 micrograms; Group 2--25 micrograms; Group 3--250 micrograms. Animals were prepared and infused, and their quarter-udder weights and DNA were determined as in Examples 3-6. Results for Group 1 are in Table 9.

                  TABLE 9                                                          ______________________________________                                         Effects of Intramammary Infusion of a Total of 12.5 Micrograms                 of bIGF-I on Quarter-Udders in Pregnant Beef Cows (Group 1)                              Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   408.4    111.7  54.9     1307                                      Mean                                                                       B.  Control Mean                                                                               369.0    102.7  48.0     1219                                      (Excipient only)                                                           C.  Mean Increase                                                                              39.4     9.0    6.9      88                                        (A - B)                                                                    D.  % Increase, 10.7     8.7    14.2     7.2                                       (A - B)/B                                                                  E.  Avg. % In-  11.0     8.8    16.0     12.5                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.01     0.003  0.03     0.2                                       % Increase, p<                                                             ______________________________________                                    

In this study, the two higher doses of bIGF-I (Groups 2-3) did not produce consistently greater growth of treatment quarters vs. control quarters. However, substantial growth of the noninfused quarters was observed. When the procedures described for Groups 1-3 were repeated, results were essentially the same. Pooling results from the original study and its replication, it was determined that both treatment and control quarter-udders had grown as follows:

                  TABLE 10                                                         ______________________________________                                                                              Com-                                      Doses   Controls       Treatment     bined                                     ______________________________________                                         Medium vs.                                                                             +27%,    p < 0.08  +23.1%,                                                                               p < 0.12                                                                              +35%                                  Low                                                                            High vs.                                                                               +34.4%,  p < 0.08  +31.5%,                                                                               p < 0.09                                                                              +33%                                  Medium                                                                         High vs.                                                                               +71.3%,  p < 0.007 +62%,  p < 0.01                                                                              +67%                                  Low                                                                            ______________________________________                                    

The above increases in growth of the control quarter-udders occurred even though plasma levels of bIGF-I did not increase significantly during the study. Results were essentially the same when these tests were repeated using other pregnant, nonlactating beef cows groups on the basis of essentially equal beginning udder volumes to remove that variable as much as possible from the test results.

EXAMPLES 17-19

When dairy or beef heifers (either pregnant or non-pregnant) or pregnant cows within the last 25-60 days of gestation are infused according to the procedure in Examples 14-16 with a total of 125 micrograms, 1.25 milligrams or 12.5 milligrams of bovine insulin-like growth factor-II purified essentially free from all other bovine peptides as in Example 1 of U.S. patent application 888,996 field Jul. 31, 1986 corresponding to European Patent Appln. 86870128.5, both incorporated herein by reference, the results are essentially the same as in Examples 14-16, i.e., substantial increases in the weights and DNA of the treated quarter-udders.

C. Combinations of IGF's and EGF's EXAMPLE 20

30 mixed-breed sheep within their last 35-45 days of gestation were fed a ration of alfalfa hay and sheep chow and administered 2.5 ml of an excipient (a Freund's emulsion of the kind used in Examples 1-2 for 15 sheep; physiological (0.9%) saline solution for the other 15) into each half udder by intramammary infusion through the streak canal on days 1, 3, 5, 7 and 9 of this study. Infusions were carried out using a 3.2 centimeter long, 16 gauge, blunt-tipped Teflon sheath from a C. R. Bard, Inc. A-cath cannula for placement of indwelling catheters. Udder halves in each animal were randomly assigned to treatment in which the excipient contained additionally 2.5 micrograms of mouse EGF of the kind used in Examples 1-2 and 2.5 micrograms of human IGF-I prepared by expression of recombinant DNA and sold by AMgen Biological Corp., Thousand Oaks, Calif. (Catalog No. 04111, Lot 407; over 90% pure as determined by HPLC). The other udder half in each animal was assigned to control in which the excipient only was infused. Prior to treatment, each animal was teat-dipped for 7 consecutive days and each teat was pre-cleaned with 70% ethanol in water on the day of treatment.

On day 13 the sheep were sacrificed and their mammary glands excised. Each udder (milked out if necessary) was skinned and divided along the median suspensory ligament into right and left udder halves. Each half-udder was homogenized with 4 times its weight of water, and the total homogenate volume of each was measured.

To determine dry weight of each half-udder, three 10 ml aliquots of a 1:5 diluted homogenate were placed in pre-weighed pans, dried overnight at 60° and then dried and weighed to a consistent value.

To detrmine dry fat-free tissue weight of each half-udder, three 5 ml aliquots of the undited homogenate were extracted by the method of Anderson, 41 J. Anim. Sci. 118 (1975) except that samples were placed in preweighed 25×150 mm glass centrifuge tubes and extracted overnight with 10 ml of ethanol:ether (3:1), then centrifuged (5 min at 500 rpm) and the supernatant aspirated; an additional 10 ml aliquot of ethanol:ether was added for a second extraction; and the sample was dried under nitrogen and weighed until a constant value was obtained.

DNA in each half-udder was determined by the method of Burton, Biochemistry 62315 (1956) using an assay solution of 15% trichloroacetic acid (TCA) in 2N HCl. In these determinations, aliquots of gland homogenate were thawed, diluted 1:5 with water and rehomogenized. Using triplicate 0.5 ml aliquots of these homogenates, each aliquot was mixed with 2 ml of the assay solution. After 30 min, the samples were centrifuged for 10 min at 3000 rpm and the resulting pellets were washed with 2 ml of a 10% solution of TCA in distilled water. After recentrifugation, the resulting pellets were disrupted in 2 ml of 0.5N perchloric acid and heated for 30 min at 70° to extract DNA. Samples were centrifuged and 1 ml of each resulting supernatant was placed in a 12×75 mm tube. After addition of 2 ml of a solution of 1.5 g diphenylamine and 1.5 ml H₂ SO₄ in 100 ml glacial acetic acid (and 0.1 ml of 1.6% aqueous acetaldehyde per 20 ml reagent just prior to use), the samples were vortexed and incubated overnight at 20°. Calf thymus DNA was the standard.

                  TABLE 11                                                         ______________________________________                                         Effects of Intramammary Infusion of a Combination of mEGF                      and hIGF-I on Half-Udders in Pregnant Sheep                                              Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   277.3    73.6   75.2     1021.2                                    Mean                                                                       B.  Control Mean                                                                               264.7    66.2   56.4     849.5                                     (Excipient only)                                                           C.  Mean Increase                                                                              12.5     7.4    18.8     171.7                                     (A - B)                                                                    D.  % Increase, 4.7      11.0   33.0     20.2                                      (A - B)/B                                                                  E.  Sig. Level of                                                                              0.016    0.03   0.001    0.002                                     % Increase, p<                                                             ______________________________________                                    

The data in Table 11 shows that DNA and wet, dry and dry fat-free weights of the half-udders treated in accordance with this invention ere substantially increased relative to the untreated half-udders in the same animals, and at exceptionally high levels of statistical significance.

EXAMPLE 21

8 non-pregnant Holstein heifers about 18 months of age were tested for the effects of intramammary infusion of a combination of bovine IGF-I and human EGF according to the procedures used in Examples 14-16 with the exceptions that (A) the volume of excipient in each infusion was 2.5 ml, (B) each treatment infusion contained 6.25 micrograms of bIGF-I and 625 micrograms of hEGF of the kinds used in Examples 14-16 and 1-2, respectively, and (C) DNA's were not determined. Results are in Table 12.

                  TABLE 12                                                         ______________________________________                                         Effects of Intramammary Infusion of a Combination of hEGF                      and bIGF-I on Quarter-Udders in Holstein Heifers                                          Wet     Dry        Dry Fat-Free                                                Weight, g                                                                              Weight, g  Weight, g                                        ______________________________________                                         A.  Treatment    205.1     93.2     10.7                                           Mean                                                                       B.  Control Mean 188.2     89.0     9.5                                            (Excipient only)                                                           C.  Mean Increase                                                                               16.9      4.2      1.2                                            (A - B)                                                                    D.  % Increase,  8.9       4.7      12.1                                           (A - B)/B                                                                  E.  Avg. % In-   11.3      7.7      18.8                                           crease/Animal                                                              F.  Sig. Level of                                                                               0.06      0.2      0.09                                           % Increase, p<                                                             ______________________________________                                    

The data in Table 12 show that the wet, dry and dry fat-free weights of Holstein heifer quarter-udders treated in accordance with this invention were substantially greater than their laterally-opposite quarter-udders that received excipient only, and at high levels of statistical significance.

EXAMPLE 22

The effects of intramammary infusion of a combination of bovine IGF-I and human EGF on 8 pregnant, non-lactating, cross-bred beef cows within their last 40-80 days of gestation were determined by the procedures described in Examples 14-16. Each treatment infusion contained 25 micrograms of hEGF of the kind used in Examples 1-2 and 250 micrograms of bIGF-I of the kind used in Examples 14-16. Results are in Table 13.

                  TABLE 13                                                         ______________________________________                                         Effects of Intramammary Infusion of a Combination of                           bIGF-I ( a Total of 1.25 Milligrams) and hEGF (a Total of                      125 Micrograms) on Quarter-Udders in Pregnant Beef Cattle                                Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   496.1    156.4  72.0     1392                                      Mean                                                                       B.  Control Mean                                                                               474.0    144.0  60.7     1243                                      (Excipient only)                                                           C.  Mean Increase                                                                              22.1     12.4   11.3     149                                       (A - B)                                                                    D.  % Increase, 4.7      8.6    18.7     12.0                                      (A - B)/B                                                                  E.  Avg. % In-  8.2      13.0   11.0     12.0                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.1      0.03   0.08     0.15                                      % Increase, p<                                                             ______________________________________                                    

As shown in Table 13, quarter-udders receiving the combination of bIGF-I and hEGF were consistently heavier and contained more DNA than their laterally-opposite control quarters, and at high levels of statistical significance.

EXAMPLES 23-24

18 pregnant Holstein heifers within their last 40-60 days of expected calving were housed in a free-stall facility, fed a ration of alfalfa hay and pelleted concentrate and administered 10 ml of an excipient (sterile sesame oil) into each quarter-udder by intramammary infusion through the steak canal every third day for the number of treatments shown below. The heifers in Groups 1 and 3 were treated no later than their fifth day before parturition; treatments of those in Groups 2 and 4 were continued into their last five days. Treatments containing a mitogenic substance were administered to both quarter-udders on one side of each animal. Excipient only was administered to both quarter-udders on the opposite side of that animal. All infusions were carried out with a Jorgensen Laboratories infusion canula of the kind used in Examples 1-2. Each teat was sprayed with 70% ethanol and wiped dry prior to treatment, and dipped with an iodine solution following treatment.

    ______________________________________                                         No. of     Mitogenic Substance                                                                           No. of Treatments                                    Group  Heifers In The Excipient                                                                              Range   Avg.                                     ______________________________________                                         1      4       hEGF & IGF-I*  10      10                                                      (0.25 mg each)                                                  2      5       hEGF & IGF-I*  7-20    14                                                      (0.25 mg each)                                                  3      5       BST** (50 mg)  10-20   12                                       4      4       BST** (50 mg)  4-16    9                                        ______________________________________                                          *Obtained as in Examples 1-2 and 14-16, respectively, solubilized (62.5        micrograms/ml of each) in sterile, injectablegrade 0.9% saline containing      0.5% Tween20 and emulsified into the sterile sesame oil excipient (3:2         oil:saline) and 5% Arlacel A (Sigma Chemical Co., St. Louis, MO).              **Prepared as in Examples 40-41 and diluted to 10 mg/ml in the sesame oil      excipient. See results in Examples 42-43.                                

These animals were milked normally each a.m. and p.m. for the first 30 days after parturition, with milk production recorded separately for each quarter-udder. On average, milk production by the half-udders that had been treated in Group 2 did not exceed that of their control half-udders.

                  TABLE 14                                                         ______________________________________                                         Effects of Intramammary Infusion                                               of a Combination of hEGF and IGF-I on Quarter-Udders                           in Pregnant Heifers (Group 1)                                                  Average Milk                                                                   Production, kg/day                                                             Treated  Control    % Increase,                                                                               Sig. Level of                                   Side (A) Side (B)   (A - B)/B  Increase, p<                                    ______________________________________                                         10.0     9.0        11         0.14                                            ______________________________________                                    

As shown in Table 14, quarter-udders infused with a combination of hEGF and IGF-I no later than the fifth day before parturition produced, on average, substantially more milk than their laterally-opposite quarters that received excipient only.

D. Prostaglandins EXAMPLES 25-28

24 pregnant, non-lactating, cross-bred beef cows in their last 45-105 days of gestation were housed in a free-stall facility, fed a ration of alfalfa hay and pelleted concentrate, and administered 5 ml of an excepient (MCT-Oil, a Mead Johnson Corp. medium chain triglyceride which is a lipid fraction of coconut oil consisting primarily of triglycerides of C₈ and C₁₀ fatty acids as follows: C₈ -67%; C₁₀ -23%; <C₈ -6%; >C₁₀ -4%) into each quarter-udder by intramammary infusion through the streak cannal on days 1, 3, 5, 7 and 9 of this study. The 48 front and rear udder halves were randomly divided into 4 groups, with one quarter of each udder half treated and its laterally opposite quarter-udder used as a control. In the treatment infusions, the excipient contained Prostaglandin (PG) E₁ or E₂ from Sigma Chemical Co., St. Louis, Mo. (Catalog Nos. 86F-0406 and -0404). The amounts of PG in each infusion were: Group 1--87.5 micrograms of E₂ ; Group 2--875 micrograms of E₂ ; Group 3--87.5 micrograms of E₁ ; Group 4--875 micrograms of E₁. Animals were prepared and infused as in Examples 23-24; the effects were determined as in Examples 1-2. Results for Groups 1-4 are in Tables 15-18, respectively.

                  TABLE 15                                                         ______________________________________                                         Effects of Intramammary Infusion of Prostaglandin E.sub.2 (a Total             of 0.4375 Milligrams) on Quarter-Udders in Pregnant Beef                       Cattle (Group 1)                                                                         Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   1966.9   525.5  351.8    5203                                      Mean                                                                       B.  Control Mean                                                                               1735.5   484.9  297.8    4724                                      (Excipient only)                                                           C.  Mean Increase                                                                              231.4    40.6   54.0     479                                       (A - B)                                                                    D.  % Increase  13.3     8.3    18.1     10.1                                      (A - B)/B                                                                  E.  Sig. Level of                                                                              0.01     0.04   0.18     0.02                                      % Increase, p<                                                             ______________________________________                                    

                  TABLE 16                                                         ______________________________________                                         Effects of Intramammary Infusion of Prostaglandin E.sub.2 (a Total             of 0.4375 Milligrams) on Quarter-Udders in Pregnant Beef                       Cattle (Group 2)                                                                         Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   1030.8   312.7  194.5    3397                                      Mean                                                                       B.  Control Mean                                                                               742.0    219.0  144.3    2348                                      (Excipient only)                                                           C.  Mean Increase                                                                              288.8    93.7   50.2     1049                                      (A - B)                                                                    D.  % Increase, 38.9     42.8   34.8     44.6                                      (A - B)/B                                                                  E.  Sig. Level of                                                                              0.0003   0.0001 0.004    0.001                                     % Increase, p<                                                             ______________________________________                                    

                  TABLE 17                                                         ______________________________________                                         Effects of Intramammary Infusion of Prostaglandin E.sub.1 (a Total             of 0.4375 Milligrams) on Quarter-Udders in Pregnant Beef                       Cattle (Group 3)                                                                         Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   972.5    259.3  180.9    2881                                      Mean                                                                       B.  Control Mean                                                                               778.0    210.6  200.3    2284                                      (Excipient only)                                                           C.  Mean Increase                                                                              194.5    48.7   (19.4)   597                                       (A - B)                                                                    D.  % Increase, 25.0     23.0   (9.7)    26                                        (A - B)/B                                                                  E.  Sig. Level of                                                                              0.002    0.002  0.58     0.07                                      % Increase, p<                                                             ______________________________________                                    

                  TABLE 18                                                         ______________________________________                                         Effects of Intramammary Infusion of Prostaglandin E.sub.1 (a Total             of 0.4375 Milligrams) on Quarter-Udders in Pregnant Beef                       Cattle (Group 4)                                                                         Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   1435.5   379.6  247.7    4218                                      Mean                                                                       B.  Control Mean                                                                               949.3    268.2  189.0    2792                                      (Excipient only)                                                           C.  Mean Increase                                                                              486.2    111.4  58.7     1426                                      (A - B)                                                                    D.  % Increase  51.2     41.5   31.0     51.1                                      (A - B)/B                                                                  E.  Sig. Level of                                                                              0.03     0.02   0.07     0.06                                      % Increase, p<                                                             ______________________________________                                    

As shown in Tables 15-18, quarter-udders receiving the prostaglandins were consistently heavier and contained more DNA than their laterally-opposite control quarters that received excipient only, and at generally very high levels of statistical significance.

E. Transforming Growth Factors EXAMPLES 29-32

When dairy or beef heifers (either pregnant or non-pregnant) or pregnant dairy or beef cows within their last 25-60 days of gestation are infused using the procedures and dosages of Examples 3-6 with human alpha-type transforming growth factor obtained from Bachem Inc. Fine Chemicals, Torrance, Calif. (Catalog #PGRO-30), results are essentially the same, i.e., substantial and statistically significant increases in the weights and DNA of the treated quarter-udders.

F. Mammary-Derived Growth Factors EXAMPLES 33-36

When dairy or beef heifers (either pregnant or nonpregnant) or pregnant beef or dairy cows within their last 25-60 days of gestation are infused using the procedures and dosages of Examples 3-6 with MDGF₁ or MDGF₂ obtained by purification according to the aforecited Kidwell et al publications, results are essentially the same, i.e., substantial and statistically substantial increases in the weight and DNA of the treated quarter-udders.

G. Insulin EXAMPLES 37-39

When dairy or beef heifers (either pregnant or non-pregnant) or pregnant beef or dairy cows within their last 25-60 days of gestation are infused according to the procedures of Examples 3-6 with 25, 100 or 250 mg per infusion of bovine pancreas insulin from Sigma Chemical Co., St. Louis, Mo. (Catalog #I-5500; 24 IU/mg), results are similar, i.e., substantial and statistically significant increases in the weights and DNA of the treated quarter-udders.

H. Somatotropins EXAMPLES 40-41

24 pregnant, non-lactating, cross-bred beef cows in their last 40-80 days of gestation ere divided into 2 groups and tested for the effects of intramammary infusion using the procedures of Examples 3-6 except that (A) the volume of excipient in each infusion was 5 ml and (B) each treatment infusion contained a 1% zinc salt of an N-methionyl bovine somatotropin (BST) (Group 1--100 mg; Group 2--40 mg) prepared by expression of recombinant DNA and purified essentially as described in Example 1A of U.S. patent application No. 787,873 field Oct. 16, 1985 based on European Patent Appln. 177,478 published Apr. 9, 1986, both incorporated here by reference. Results are in Tables 19-20.

                  TABLE 19                                                         ______________________________________                                         Effects of Intramammary Infusion of a Total of 500 Milligrams                  of BST on Quarter-Udders in Pregnant Beef Cows (Group 1)                                 Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   790.1    207.6  146.7    2185                                      Mean                                                                       B.  Control Mean                                                                               736.6    190.6  141.5    2054                                      (Excipient only)                                                           C.  Mean Increase                                                                              53.5     17.0   5.2      131                                       (A - B)                                                                    D.  % Increase, 7.3      8.9    3.6      6.4                                       (A - B)/B                                                                  E.  Avg. % In-  9.8      10.7   7.9      10.5                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.004    0.03   0.18     0.3                                       % Increase, p<                                                             ______________________________________                                    

                  TABLE 20                                                         ______________________________________                                         Effects of Intramammary Infusion of a Total of 200 Milligrams                  of BST on Quarter-Udders in Pregnant Beef Cows (Group 2)                                 Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   396.9    96.4   49.5     1371                                      Mean                                                                       B.  Control Mean                                                                               345.4    85.1   44.8     1299                                      (Excipient only)                                                           C.  Mean Increase                                                                              51.5     11.3   4.7      72                                        (A - B)                                                                    D.  % Increase, 14.9     13.3   10.5     5.5                                       (A - B)/B                                                                  E.  Avg. % In-  13.4     10.7   7.8      15.8                                      crease/Animal                                                              F.  Sig. Level of                                                                              0.007    0.06   0.06     0.1                                       % Increase, p<                                                             ______________________________________                                    

The data in Tables 19-20 show that the increases in DNA and wet, dry and dry fat-free weights of pregnant beef cow quarter-udders treated in accordance with this invention were substantially greater than those of their laterally-opposite quarter-udders that received excipient only, and that the differences between treatment and control increases are at high levels of statistical significance.

EXAMPLES 42-43

Shown in Table 21 are the milk production results obtained with the heifers of Group 3 in Examples 23-24. On average, milk production by the half-udders that had been treated in Group 4 of Examples 23-24 slightly exceeded (2%, p<0.4) that of their control half-udders.

                  TABLE 21                                                         ______________________________________                                         Effects of Intramammary Infusion of BST on Quarter-                            Udders in Pregnant Holstein Heifers (Group 4)                                  Average Milk                                                                   Production, kg/day                                                             Treated  Control    % Increase,                                                                               Sig. Level of                                   Side (A) Side (B)   (A - B)/B  Increase, p<                                    ______________________________________                                         10.9     9.8        11         0.15                                            ______________________________________                                    

As shown in Table 21, quarter-udders infused with BST no later than the fifth day before parturition produced, on average, substantially more milk than their laterally-opposite quarters that received excipient only.

I. Bovine Placental Lactogens EXAMPLES 44-46

When dairy or beef heifers (either pregnant or non-pregnant) or pregnant beef or dairy cows within their last 40-80 days of gestation re infused according to the procedures of Examples 3-6 with a total of 0.25, 10 or 250 milligrams of natural bovine placental lactogen purified by the method of Byatt, 119 Endocrin. 1343-50 (1986), results are very similar, i.e., substantial and statistically significant increases in the weights and DNA of the treated quarter-udders.

COMPARATIVE EXAMPLES--OVINE PROLACTINS

16 pregnant, non-lactating, cross-bred beef cows in their last 30-105 days of gestation were divided into 2 groups and tested for the effects of intramammary infusion using the procedures of Examples 25-28 except that instead of a prostaglandin, each treatment infusion contained either 2 mg (Group 1) or 10 mg (Group 2) of ovine prolactin obtained from Sigma Chemical Co., St. Louis, Mo. (Lot No. 26F-0076) in 10 ml of an emulsion of 0.9% saline containing 0.5% Tween-20 in sterile sesame oil containing 5% Arlacel A (3:2 oil: saline). Results are in Tables 22-23.

                  TABLE 22                                                         ______________________________________                                         Effects of Intramammary Infusion of Ovine Prolactin                            (a Total of 10 Milligrams) on Quarter-Udders in Pregnant Beef                  Cattle (Group 4)                                                                         Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   895.3    262.7  137.8    2526                                      Mean                                                                       B.  Control Mean                                                                               889.9    257.9  136.6    2566                                      (Excipient only)                                                           C.  Mean Increase                                                                              5.4      4.8    1.2      (40)                                      (A - B)                                                                    D.  % Increase, .6       1.0    .88      (1.6)                                     (A - B)/B                                                                  E.  Sig. Level of                                                                              0.85     0.8    0.97     --                                        % Increase, p<                                                             ______________________________________                                    

                  TABLE 23                                                         ______________________________________                                         Effects of Intramammary Infusion of Ovine Prolactin                            (Total dose of 50 Milligrams) on Quarter-Udders in Pregnant Beef               Cattle (Group 2)                                                                         Wet    Dry                                                                     Weight,                                                                               Weight,  Dry Fat-Free                                                                              DNA,                                                g      g        Weight, g  mg                                        ______________________________________                                         A.  Treatment   1487.1   343.4  189.2    3672                                      Mean                                                                       B.  Control Mean                                                                               1308.5   349.0  184.5    3322                                      (Excipient only)                                                           C.  Mean Increase                                                                              178.6    (5.6)  4.7      350                                       (A - B)                                                                    D.  % Increase, 13.6     (1.6)  2.5      10.5                                      (A - B)/B                                                                  E.  Sig. Level of                                                                              0.09     --     0.7      0.27                                      % Increase, p<                                                             ______________________________________                                    

While the biological mechanisms of this invention are not fully understood, it is apparent that it can be used to provide, in accordance with conventionally recognized criteria, increases in mammary parenchyma and corresponding milk production capacity of treated animals that will persist through the animal's next lactation period, and in many cases through multiple subsequent lactations. 

We claim:
 1. A method for enhancing the proliferation of mammary parenchymal cells in a mammary gland of a female ruminant wherein a total of from about 100 micrograms to 50 milligrams of a polypeptide growth factor having a molecular weight of less than 65,000 daltons and having a direct mitogenic effect on mammary epithelial cells in said ruminant is administered to the mammary gland by intramammary infusion during gestation or between the onset of puberty and the ruminant's first gestation.
 2. The method of claim 1 wherein the polypeptide growth factor has a molecular weight of less than 23,000 daltons.
 3. The method of claim 2 wherein the polypeptide growth factor is an epidermal growth factor, insulin family growth factor or combination thereof.
 4. The method of claim 2 wherein the polypeptide growth factor is an epidermal growth factor.
 5. The method of claim 2 wherein the polypeptide growth factor is IGF-I or IGF-II.
 6. The method of claim 1 wherein said ruminant is a cow, sheep or goat.
 7. The method of claim 1 wherein the polypeptide growth factor is administered in a physiologically acceptable liquid vehicle.
 8. The method of claim 7 wherein said physiologically acceptable vehicle is selected from the group consisting of mineral oil, vegetable oil, saline solution and mixtures thereof.
 9. The method of claim 8 wherein said vegetable oil is peanut oil or sesame oil.
 10. The method of claim 7 wherein said polypeptide growth factor is administered in a unit dose of from about 2.5 micrograms to 250 micrograms per mammary gland per infusion.
 11. The method of claim 11 wherein from 1 to 5 unit doses per mammary gland are infused over a period of from 1 to about 10 days.
 12. The method of claim 11 wherein said ruminant is a cow.
 13. The method of claim 12 wherein said polypeptide growth factor is EGF, IGF-I, IGF-II, or a combination thereof.
 14. The method of claim 10 wherein said ruminant is a sheep or goat.
 15. The method of claim 10 wherein the polypeptide growth factor is administered in from 1 to about 10 ml of liquid vehicle.
 16. The method of claim 15 wherein said vehicle is substantially liquid at the body temperature of said ruminant.
 17. The method of claim 15 wherein said polypeptide growth factor is substantially soluble in said liquid vehicle.
 18. The method of claim 15 wherein the ruminant is a cow, sheep or goat.
 19. A method for enhancing the proliferation of mammary parenchymal cells in a mammary gland of a non-ruminant mammal wherein a proliferation enhancing amount of a polypeptide growth factor having a molecular weight of less than 65,000 daltons and having a direct mitogenic effect on mammary epithelial cells in said mammal is administered to the mammary gland by intramammary infusion during gestation or between the onset of puberty and the mammal's first gestation.
 20. The method of claim 19 wherein the polypeptide growth factor has a molecular weight of less than 23,000 daltons.
 21. The method of claim 20 wherein the polypeptide growth factor is an epidermal growth factor, insulin family growth factor or combination thereof.
 22. The method of claim 20 wherein the polypeptide growth factor is an epidermal growth factor.
 23. The method of claim 20 wherein the polypeptide growth factor is IGF-I or IGF-II.
 24. The method of claim 19 wherein said mammal is a swine.
 25. The method of claim 19 wherein the polypeptide growth factor is administered in a physiologically acceptable liquid vehicle.
 26. The method of claim 25 wherein said physiologically acceptable vehicle is selected from the group consisting of mineral oil, vegetable oil, saline solution and mixtures thereof.
 27. The method of claim 26 wherein said vegetable oil is peanut oil or sesame oil.
 28. The method of claim 25 wherein said polypeptide growth factor is administered in a unit dose of from about 2.5 micrograms to 250 micrograms per mammary gland per infusion.
 29. The method of claim 28 wherein from 1 to 5 unit doses per mammary gland are infused over a period of from 1 to about 10 days.
 30. The method of claim 28 wherein the mammal is a swine.
 31. The method of claim 28 wherein said polypeptide growth factor is EGF, IGF-I, IGF-II, or a combination thereof.
 32. The method of claim 31 wherein the mammal is a swine.
 33. The method of claim 28 wherein the polypeptide growth factor is administered in from 1 to about 10 ml of liquid vehicle.
 34. The method of claim 33 wherein said vehicle is substantially liquid at the body temperature of said mammal.
 35. The method of claim 33 wherein said polypeptide growth factor is substantially soluble in said liquid vehicle.
 36. The method of claim 33 wherein the mammal is a swine.
 37. A method for enhancing the proliferation of mammary parenchymal cells in a mammary gland of a female mammal wherein a proliferation enhancing amount of a polypeptide growth factor having a molecular weight of less than 65,000 daltons and having a paracrine mitogenic effect on mammary epithelial cells in said mammal is administered to the mammary gland by intramammary infusion during gestation or between the onset of puberty and the mammal's first gestation.
 38. The method of claim 37 wherein the polypeptide growth factor has a molecular weight of less than about 23,000 daltons.
 39. The method of claim 37 wherein from 10 milligrams to 500 milligrams of said polypeptide growth factor per mammary gland is administered to said mammal.
 40. The method of claim 37 wherein the polypeptide growth factor is administered in a physiologically acceptable liquid vehicle.
 41. The method of claim 40 wherein said physiologically acceptable vehicle is selected from the group consisting of mineral oil, vegetable oil, saline solution and mixtures thereof.
 42. The method of claim 41, wherein said vegetable oil is peanut oil or sesame oil.
 43. The method of claim 37 wherein the polypeptide growth factor is administered in from 1 to about 10 ml of said liquid vehicle.
 44. The method of claim 40 wherein said vehicle is substantially liquid at the body temperature of said mammal.
 45. The method of claim 43 wherein said polypeptide growth factor is substantially soluble in said liquid vehicle.
 46. The method of claim 37 wherein the polypeptide growth factor is somatotropin.
 47. The method of claim 37 wherein said mammal is a cow.
 48. The method of claim 47 wherein the polypeptide growth factor is bovine somatotropin.
 49. The method of claim 48 wherein said bovine somatotropin is administered to said dairy or beef cow in a unit dose of from about 40 milligrams to 100 milligrams per mammary gland per infusion.
 50. The method of claim 49 wherein from 1 to 5 unit doses per mammary gland are infused over a period of from 1 to about 10 days.
 51. The method of claim 37 wherein the polypeptide growth factor is a placental lactogen.
 52. The method of claim 47 wherein the polypeptide growth factor is bovine placental lactogen.
 53. The method of claim 52 wherein said bovine placental lactogen is administered in a unit dose of from about 10 milligrams to 250 milligrams per mammary gland per infusion.
 54. The method of claim 53 wherein from 1 to 5 unit doses are infused over a period of from 1 to about 10 days.
 55. The method of claim 37 wherein said mammal is a sheep, goat or swine.
 56. The method of claim 55 wherein said polypeptide growth factor is somatotropin or placental lactogen. 